Dogcows Code - chaz/tar/blob - src/misc.c

   1 /* Miscellaneous functions, not really specific to GNU tar.
   2
   3    Copyright (C) 1988, 1992, 1994, 1995, 1996, 1997, 1999, 2000, 2001,
   4    2003, 2004, 2005, 2006 Free Software Foundation, Inc.
   5
   6    This program is free software; you can redistribute it and/or modify it
   7    under the terms of the GNU General Public License as published by the
   8    Free Software Foundation; either version 2, or (at your option) any later
   9    version.
  10
  11    This program is distributed in the hope that it will be useful, but
  12    WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General
  14    Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License along
  17    with this program; if not, write to the Free Software Foundation, Inc.,
  18    51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
  19
  20 #include <system.h>
  21 #include <rmt.h>
  22 #include "common.h"
  23 #include <quotearg.h>
  24 #include <save-cwd.h>
  25 #include <xgetcwd.h>
  26 #include <unlinkdir.h>
  27 #include <utimens.h>
  28
  29 #if HAVE_STROPTS_H
  30 # include <stropts.h>
  31 #endif
  32 #if HAVE_SYS_FILIO_H
  33 # include <sys/filio.h>
  34 #endif
  35
  36 \f
  37 /* Handling strings.  */
  38
  39 /* Assign STRING to a copy of VALUE if not zero, or to zero.  If
  40    STRING was nonzero, it is freed first.  */
  41 void
  42 assign_string (char **string, const char *value)
  43 {
  44   if (*string)
  45     free (*string);
  46   *string = value ? xstrdup (value) : 0;
  47 }
  48
  49 /* Allocate a copy of the string quoted as in C, and returns that.  If
  50    the string does not have to be quoted, it returns a null pointer.
  51    The allocated copy should normally be freed with free() after the
  52    caller is done with it.
  53
  54    This is used in one context only: generating the directory file in
  55    incremental dumps.  The quoted string is not intended for human
  56    consumption; it is intended only for unquote_string.  The quoting
  57    is locale-independent, so that users needn't worry about locale
  58    when reading directory files.  This means that we can't use
  59    quotearg, as quotearg is locale-dependent and is meant for human
  60    consumption.  */
  61 char *
  62 quote_copy_string (const char *string)
  63 {
  64   const char *source = string;
  65   char *destination = 0;
  66   char *buffer = 0;
  67   int copying = 0;
  68
  69   while (*source)
  70     {
  71       int character = *source++;
  72
  73       switch (character)
  74         {
  75         case '\n': case '\\':
  76           if (!copying)
  77             {
  78               size_t length = (source - string) - 1;
  79
  80               copying = 1;
  81               buffer = xmalloc (length + 2 + 2 * strlen (source) + 1);
  82               memcpy (buffer, string, length);
  83               destination = buffer + length;
  84             }
  85           *destination++ = '\\';
  86           *destination++ = character == '\\' ? '\\' : 'n';
  87           break;
  88
  89         default:
  90           if (copying)
  91             *destination++ = character;
  92           break;
  93         }
  94     }
  95   if (copying)
  96     {
  97       *destination = '\0';
  98       return buffer;
  99     }
 100   return 0;
 101 }
 102
 103 /* Takes a quoted C string (like those produced by quote_copy_string)
 104    and turns it back into the un-quoted original.  This is done in
 105    place.  Returns 0 only if the string was not properly quoted, but
 106    completes the unquoting anyway.
 107
 108    This is used for reading the saved directory file in incremental
 109    dumps.  It is used for decoding old `N' records (demangling names).
 110    But also, it is used for decoding file arguments, would they come
 111    from the shell or a -T file, and for decoding the --exclude
 112    argument.  */
 113 int
 114 unquote_string (char *string)
 115 {
 116   int result = 1;
 117   char *source = string;
 118   char *destination = string;
 119
 120   /* Escape sequences other than \\ and \n are no longer generated by
 121      quote_copy_string, but accept them for backwards compatibility,
 122      and also because unquote_string is used for purposes other than
 123      parsing the output of quote_copy_string.  */
 124
 125   while (*source)
 126     if (*source == '\\')
 127       switch (*++source)
 128         {
 129         case '\\':
 130           *destination++ = '\\';
 131           source++;
 132           break;
 133
 134         case 'a':
 135           *destination++ = '\a';
 136           source++;
 137           break;
 138
 139         case 'b':
 140           *destination++ = '\b';
 141           source++;
 142           break;
 143
 144         case 'f':
 145           *destination++ = '\f';
 146           source++;
 147           break;
 148
 149         case 'n':
 150           *destination++ = '\n';
 151           source++;
 152           break;
 153
 154         case 'r':
 155           *destination++ = '\r';
 156           source++;
 157           break;
 158
 159         case 't':
 160           *destination++ = '\t';
 161           source++;
 162           break;
 163
 164         case 'v':
 165           *destination++ = '\v';
 166           source++;
 167           break;
 168
 169         case '?':
 170           *destination++ = 0177;
 171           source++;
 172           break;
 173
 174         case '0':
 175         case '1':
 176         case '2':
 177         case '3':
 178         case '4':
 179         case '5':
 180         case '6':
 181         case '7':
 182           {
 183             int value = *source++ - '0';
 184
 185             if (*source < '0' || *source > '7')
 186               {
 187                 *destination++ = value;
 188                 break;
 189               }
 190             value = value * 8 + *source++ - '0';
 191             if (*source < '0' || *source > '7')
 192               {
 193                 *destination++ = value;
 194                 break;
 195               }
 196             value = value * 8 + *source++ - '0';
 197             *destination++ = value;
 198             break;
 199           }
 200
 201         default:
 202           result = 0;
 203           *destination++ = '\\';
 204           if (*source)
 205             *destination++ = *source++;
 206           break;
 207         }
 208     else if (source != destination)
 209       *destination++ = *source++;
 210     else
 211       source++, destination++;
 212
 213   if (source != destination)
 214     *destination = '\0';
 215   return result;
 216 }
 217 \f
 218 /* Handling numbers.  */
 219
 220 /* Output fraction and trailing digits appropriate for a nanoseconds
 221    count equal to NS, but don't output unnecessary '.' or trailing
 222    zeros.  */
 223
 224 void
 225 code_ns_fraction (int ns, char *p)
 226 {
 227   if (ns == 0)
 228     *p = '\0';
 229   else
 230     {
 231       int i = 9;
 232       *p++ = '.';
 233
 234       while (ns % 10 == 0)
 235         {
 236           ns /= 10;
 237           i--;
 238         }
 239
 240       p[i] = '\0';
 241
 242       for (;;)
 243         {
 244           p[--i] = '0' + ns % 10;
 245           if (i == 0)
 246             break;
 247           ns /= 10;
 248         }
 249     }
 250 }
 251
 252 char const *
 253 code_timespec (struct timespec t, char sbuf[TIMESPEC_STRSIZE_BOUND])
 254 {
 255   time_t s = t.tv_sec;
 256   int ns = t.tv_nsec;
 257   char *np;
 258   bool negative = s < 0;
 259
 260   if (negative && ns != 0)
 261     {
 262       s++;
 263       ns = BILLION - ns;
 264     }
 265
 266   np = umaxtostr (negative ? - (uintmax_t) s : (uintmax_t) s, sbuf + 1);
 267   if (negative)
 268     *--np = '-';
 269   code_ns_fraction (ns, sbuf + UINTMAX_STRSIZE_BOUND);
 270   return np;
 271 }
 272 \f
 273 /* File handling.  */
 274
 275 /* Saved names in case backup needs to be undone.  */
 276 static char *before_backup_name;
 277 static char *after_backup_name;
 278
 279 /* Return 1 if FILE_NAME is obviously "." or "/".  */
 280 static bool
 281 must_be_dot_or_slash (char const *file_name)
 282 {
 283   file_name += FILE_SYSTEM_PREFIX_LEN (file_name);
 284
 285   if (ISSLASH (file_name[0]))
 286     {
 287       for (;;)
 288         if (ISSLASH (file_name[1]))
 289           file_name++;
 290         else if (file_name[1] == '.'
 291                  && ISSLASH (file_name[2 + (file_name[2] == '.')]))
 292           file_name += 2 + (file_name[2] == '.');
 293         else
 294           return ! file_name[1];
 295     }
 296   else
 297     {
 298       while (file_name[0] == '.' && ISSLASH (file_name[1]))
 299         {
 300           file_name += 2;
 301           while (ISSLASH (*file_name))
 302             file_name++;
 303         }
 304
 305       return ! file_name[0] || (file_name[0] == '.' && ! file_name[1]);
 306     }
 307 }
 308
 309 /* Some implementations of rmdir let you remove '.' or '/'.
 310    Report an error with errno set to zero for obvious cases of this;
 311    otherwise call rmdir.  */
 312 static int
 313 safer_rmdir (const char *file_name)
 314 {
 315   if (must_be_dot_or_slash (file_name))
 316     {
 317       errno = 0;
 318       return -1;
 319     }
 320
 321   return rmdir (file_name);
 322 }
 323
 324 /* Remove FILE_NAME, returning 1 on success.  If FILE_NAME is a directory,
 325    then if OPTION is RECURSIVE_REMOVE_OPTION is set remove FILE_NAME
 326    recursively; otherwise, remove it only if it is empty.  If FILE_NAME is
 327    a directory that cannot be removed (e.g., because it is nonempty)
 328    and if OPTION is WANT_DIRECTORY_REMOVE_OPTION, then return -1.
 329    Return 0 on error, with errno set; if FILE_NAME is obviously the working
 330    directory return zero with errno set to zero.  */
 331 int
 332 remove_any_file (const char *file_name, enum remove_option option)
 333 {
 334   /* Try unlink first if we cannot unlink directories, as this saves
 335      us a system call in the common case where we're removing a
 336      non-directory.  */
 337   bool try_unlink_first = cannot_unlink_dir ();
 338
 339   if (try_unlink_first)
 340     {
 341       if (unlink (file_name) == 0)
 342         return 1;
 343
 344       /* POSIX 1003.1-2001 requires EPERM when attempting to unlink a
 345          directory without appropriate privileges, but many Linux
 346          kernels return the more-sensible EISDIR.  */
 347       if (errno != EPERM && errno != EISDIR)
 348         return 0;
 349     }
 350
 351   if (safer_rmdir (file_name) == 0)
 352     return 1;
 353
 354   switch (errno)
 355     {
 356     case ENOTDIR:
 357       return !try_unlink_first && unlink (file_name) == 0;
 358
 359     case 0:
 360     case EEXIST:
 361 #if defined ENOTEMPTY && ENOTEMPTY != EEXIST
 362     case ENOTEMPTY:
 363 #endif
 364       switch (option)
 365         {
 366         case ORDINARY_REMOVE_OPTION:
 367           break;
 368
 369         case WANT_DIRECTORY_REMOVE_OPTION:
 370           return -1;
 371
 372         case RECURSIVE_REMOVE_OPTION:
 373           {
 374             char *directory = savedir (file_name);
 375             char const *entry;
 376             size_t entrylen;
 377
 378             if (! directory)
 379               return 0;
 380
 381             for (entry = directory;
 382                  (entrylen = strlen (entry)) != 0;
 383                  entry += entrylen + 1)
 384               {
 385                 char *file_name_buffer = new_name (file_name, entry);
 386                 int r = remove_any_file (file_name_buffer,
 387                                          RECURSIVE_REMOVE_OPTION);
 388                 int e = errno;
 389                 free (file_name_buffer);
 390
 391                 if (! r)
 392                   {
 393                     free (directory);
 394                     errno = e;
 395                     return 0;
 396                   }
 397               }
 398
 399             free (directory);
 400             return safer_rmdir (file_name) == 0;
 401           }
 402         }
 403       break;
 404     }
 405
 406   return 0;
 407 }
 408
 409 /* Check if FILE_NAME already exists and make a backup of it right now.
 410    Return success (nonzero) only if the backup is either unneeded, or
 411    successful.  For now, directories are considered to never need
 412    backup.  If THIS_IS_THE_ARCHIVE is nonzero, this is the archive and
 413    so, we do not have to backup block or character devices, nor remote
 414    entities.  */
 415 bool
 416 maybe_backup_file (const char *file_name, bool this_is_the_archive)
 417 {
 418   struct stat file_stat;
 419
 420   /* Check if we really need to backup the file.  */
 421
 422   if (this_is_the_archive && _remdev (file_name))
 423     return true;
 424
 425   if (stat (file_name, &file_stat))
 426     {
 427       if (errno == ENOENT)
 428         return true;
 429
 430       stat_error (file_name);
 431       return false;
 432     }
 433
 434   if (S_ISDIR (file_stat.st_mode))
 435     return true;
 436
 437   if (this_is_the_archive
 438       && (S_ISBLK (file_stat.st_mode) || S_ISCHR (file_stat.st_mode)))
 439     return true;
 440
 441   assign_string (&before_backup_name, file_name);
 442
 443   /* A run situation may exist between Emacs or other GNU programs trying to
 444      make a backup for the same file simultaneously.  If theoretically
 445      possible, real problems are unlikely.  Doing any better would require a
 446      convention, GNU-wide, for all programs doing backups.  */
 447
 448   assign_string (&after_backup_name, 0);
 449   after_backup_name = find_backup_file_name (file_name, backup_type);
 450   if (! after_backup_name)
 451     xalloc_die ();
 452
 453   if (rename (before_backup_name, after_backup_name) == 0)
 454     {
 455       if (verbose_option)
 456         fprintf (stdlis, _("Renaming %s to %s\n"),
 457                  quote_n (0, before_backup_name),
 458                  quote_n (1, after_backup_name));
 459       return true;
 460     }
 461   else
 462     {
 463       /* The backup operation failed.  */
 464       int e = errno;
 465       ERROR ((0, e, _("%s: Cannot rename to %s"),
 466               quotearg_colon (before_backup_name),
 467               quote_n (1, after_backup_name)));
 468       assign_string (&after_backup_name, 0);
 469       return false;
 470     }
 471 }
 472
 473 /* Try to restore the recently backed up file to its original name.
 474    This is usually only needed after a failed extraction.  */
 475 void
 476 undo_last_backup (void)
 477 {
 478   if (after_backup_name)
 479     {
 480       if (rename (after_backup_name, before_backup_name) != 0)
 481         {
 482           int e = errno;
 483           ERROR ((0, e, _("%s: Cannot rename to %s"),
 484                   quotearg_colon (after_backup_name),
 485                   quote_n (1, before_backup_name)));
 486         }
 487       if (verbose_option)
 488         fprintf (stdlis, _("Renaming %s back to %s\n"),
 489                  quote_n (0, after_backup_name),
 490                  quote_n (1, before_backup_name));
 491       assign_string (&after_backup_name, 0);
 492     }
 493 }
 494
 495 /* Depending on DEREF, apply either stat or lstat to (NAME, BUF).  */
 496 int
 497 deref_stat (bool deref, char const *name, struct stat *buf)
 498 {
 499   return deref ? stat (name, buf) : lstat (name, buf);
 500 }
 501
 502 /* Set FD's (i.e., FILE's) access time to TIMESPEC[0].  If that's not
 503    possible to do by itself, set its access and data modification
 504    times to TIMESPEC[0] and TIMESPEC[1], respectively.  */
 505 int
 506 set_file_atime (int fd, char const *file, struct timespec const timespec[2])
 507 {
 508 #ifdef _FIOSATIME
 509   if (0 <= fd)
 510     {
 511       struct timeval timeval;
 512       timeval.tv_sec = timespec[0].tv_sec;
 513       timeval.tv_usec = timespec[0].tv_nsec / 1000;
 514       if (ioctl (fd, _FIOSATIME, &timeval) == 0)
 515         return 0;
 516     }
 517 #endif
 518
 519   return futimens (fd, file, timespec);
 520 }
 521
 522 /* A description of a working directory.  */
 523 struct wd
 524 {
 525   char const *name;
 526   int saved;
 527   struct saved_cwd saved_cwd;
 528 };
 529
 530 /* A vector of chdir targets.  wd[0] is the initial working directory.  */
 531 static struct wd *wd;
 532
 533 /* The number of working directories in the vector.  */
 534 static size_t wds;
 535
 536 /* The allocated size of the vector.  */
 537 static size_t wd_alloc;
 538
 539 /* DIR is the operand of a -C option; add it to vector of chdir targets,
 540    and return the index of its location.  */
 541 int
 542 chdir_arg (char const *dir)
 543 {
 544   if (wds == wd_alloc)
 545     {
 546       if (wd_alloc == 0)
 547         {
 548           wd_alloc = 2;
 549           wd = xmalloc (sizeof *wd * wd_alloc);
 550         }
 551       else
 552         wd = x2nrealloc (wd, &wd_alloc, sizeof *wd);
 553
 554       if (! wds)
 555         {
 556           wd[wds].name = ".";
 557           wd[wds].saved = 0;
 558           wds++;
 559         }
 560     }
 561
 562   /* Optimize the common special case of the working directory,
 563      or the working directory as a prefix.  */
 564   if (dir[0])
 565     {
 566       while (dir[0] == '.' && ISSLASH (dir[1]))
 567         for (dir += 2;  ISSLASH (*dir);  dir++)
 568           continue;
 569       if (! dir[dir[0] == '.'])
 570         return wds - 1;
 571     }
 572
 573   wd[wds].name = dir;
 574   wd[wds].saved = 0;
 575   return wds++;
 576 }
 577
 578 /* Change to directory I.  If I is 0, change to the initial working
 579    directory; otherwise, I must be a value returned by chdir_arg.  */
 580 void
 581 chdir_do (int i)
 582 {
 583   static int previous;
 584
 585   if (previous != i)
 586     {
 587       struct wd *prev = &wd[previous];
 588       struct wd *curr = &wd[i];
 589
 590       if (! prev->saved)
 591         {
 592           int err = 0;
 593           prev->saved = 1;
 594           if (save_cwd (&prev->saved_cwd) != 0)
 595             err = errno;
 596           else if (0 <= prev->saved_cwd.desc)
 597             {
 598               /* Make sure we still have at least one descriptor available.  */
 599               int fd1 = prev->saved_cwd.desc;
 600               int fd2 = dup (fd1);
 601               if (0 <= fd2)
 602                 close (fd2);
 603               else if (errno == EMFILE)
 604                 {
 605                   /* Force restore_cwd to use chdir_long.  */
 606                   close (fd1);
 607                   prev->saved_cwd.desc = -1;
 608                   prev->saved_cwd.name = xgetcwd ();
 609                 }
 610               else
 611                 err = errno;
 612             }
 613
 614           if (err)
 615             FATAL_ERROR ((0, err, _("Cannot save working directory")));
 616         }
 617
 618       if (curr->saved)
 619         {
 620           if (restore_cwd (&curr->saved_cwd))
 621             FATAL_ERROR ((0, 0, _("Cannot change working directory")));
 622         }
 623       else
 624         {
 625           if (i && ! ISSLASH (curr->name[0]))
 626             chdir_do (i - 1);
 627           if (chdir (curr->name) != 0)
 628             chdir_fatal (curr->name);
 629         }
 630
 631       previous = i;
 632     }
 633 }
 634 \f
 635 void
 636 close_diag (char const *name)
 637 {
 638   if (ignore_failed_read_option)
 639     close_warn (name);
 640   else
 641     close_error (name);
 642 }
 643
 644 void
 645 open_diag (char const *name)
 646 {
 647   if (ignore_failed_read_option)
 648     open_warn (name);
 649   else
 650     open_error (name);
 651 }
 652
 653 void
 654 read_diag_details (char const *name, off_t offset, size_t size)
 655 {
 656   if (ignore_failed_read_option)
 657     read_warn_details (name, offset, size);
 658   else
 659     read_error_details (name, offset, size);
 660 }
 661
 662 void
 663 readlink_diag (char const *name)
 664 {
 665   if (ignore_failed_read_option)
 666     readlink_warn (name);
 667   else
 668     readlink_error (name);
 669 }
 670
 671 void
 672 savedir_diag (char const *name)
 673 {
 674   if (ignore_failed_read_option)
 675     savedir_warn (name);
 676   else
 677     savedir_error (name);
 678 }
 679
 680 void
 681 seek_diag_details (char const *name, off_t offset)
 682 {
 683   if (ignore_failed_read_option)
 684     seek_warn_details (name, offset);
 685   else
 686     seek_error_details (name, offset);
 687 }
 688
 689 void
 690 stat_diag (char const *name)
 691 {
 692   if (ignore_failed_read_option)
 693     stat_warn (name);
 694   else
 695     stat_error (name);
 696 }
 697
 698 void
 699 write_fatal_details (char const *name, ssize_t status, size_t size)
 700 {
 701   write_error_details (name, status, size);
 702   fatal_exit ();
 703 }
 704
 705 /* Fork, aborting if unsuccessful.  */
 706 pid_t
 707 xfork (void)
 708 {
 709   pid_t p = fork ();
 710   if (p == (pid_t) -1)
 711     call_arg_fatal ("fork", _("child process"));
 712   return p;
 713 }
 714
 715 /* Create a pipe, aborting if unsuccessful.  */
 716 void
 717 xpipe (int fd[2])
 718 {
 719   if (pipe (fd) < 0)
 720     call_arg_fatal ("pipe", _("interprocess channel"));
 721 }
 722
 723 /* Return PTR, aligned upward to the next multiple of ALIGNMENT.
 724    ALIGNMENT must be nonzero.  The caller must arrange for ((char *)
 725    PTR) through ((char *) PTR + ALIGNMENT - 1) to be addressable
 726    locations.  */
 727
 728 static inline void *
 729 ptr_align (void *ptr, size_t alignment)
 730 {
 731   char *p0 = ptr;
 732   char *p1 = p0 + alignment - 1;
 733   return p1 - (size_t) p1 % alignment;
 734 }
 735
 736 /* Return the address of a page-aligned buffer of at least SIZE bytes.
 737    The caller should free *PTR when done with the buffer.  */
 738
 739 void *
 740 page_aligned_alloc (void **ptr, size_t size)
 741 {
 742   size_t alignment = getpagesize ();
 743   size_t size1 = size + alignment;
 744   if (size1 < size)
 745     xalloc_die ();
 746   *ptr = xmalloc (size1);
 747   return ptr_align (*ptr, alignment);
 748 }